Consider the diagram and the paragraph…

Maths Questions

Consider the diagram and the paragraph proof below. Given: Right triangle ABC as shown, where CD is an altitude of the triangle. Prove: (a^2 + b^2 = c^2). Since triangles ABC and CBD both have a right angle and share angle B, they are similar by AA. Similarly, triangles ABC and ACD both have a right angle and share angle A, so they are also similar by AA. The proportions are true because they are ratios of corresponding parts of similar triangles. The two proportions can be rewritten as (a^2 = cf) and (b^2 = ce). Adding (b^2) to both sides of the first equation (a^2 = cf) leads to the equation (a^2 + b^2 = cf + b^2). Since (b^2) is equal to (ce), we can substitute (ce) into the right side of the equation for (b^2), resulting in (a^2 + b^2 = cf + ce). Applying the distributive property gives us (a^2 + b^2 = c(f + e)). What is the last sentence of the proof? Is it: Because (f + e = 1), (a^2 + b^2 = c^2); Because (f + e = c), (a^2 + b^2 = c^2); Because (a^2 + b^2 = c^2), (f + e = c); or Because (a^2 + b^2 = c^2), (f + e = 1)?

Answer

Given: Right ‚ñ≥ABC where CD is an altitude of the triangle. We aim to prove that a^2 + b^2 = c^2. Since ‚ñ≥ABC and ‚ñ≥CBD share a right angle and angle B, the triangles are similar by AA. Similarly, ‚ñ≥ABC and ‚ñ≥ACD also have a right angle and angle A in common, confirming their similarity by AA. The proportions c/a and a/f hold true as they represent ratios of corresponding parts of similar triangles. These can be expressed as a^2 = cf and b^2 = ce. Adding b^2 to both sides of the first expression a^2 = cf yields a^2 + b^2 = cf + b^2. Substituting ce for b^2 allows us to write a^2 + b^2 = cf + ce. Utilizing the converse of the distributive property gives us a^2 + b^2 = c(f + e). The concluding statement of the proof is Because f + e = c, a^2 + b^2 = c^2.

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